The Four Branches of the Mabinogi, the great medieval Welsh prose tales, open in Dyfed, and their prince, Pwyll, keeps his chief court at Arberth, the modern Narberth. The storyteller clearly knew this corner of west Wales.
Near the court was a mound, Gorsedd Arberth, with a rule attached: any man of royal blood who sat on it would not leave without either receiving wounds or blows or seeing a wonder. Pwyll, after a feast, went up and sat on it. What he saw was a woman in shining gold on a great pale white horse, riding at a slow, steady pace along the road past the mound. He sent a man after her on foot, then on the fastest horse in the court, and the harder they rode the further ahead she was, though she never seemed to hurry. On the third day Pwyll rode after her himself and, getting nowhere, called out to her to stop for the sake of the man she loved best. She stopped at once and asked why he had not asked sooner. She was Rhiannon, and she had come for him.
Arberth recurs. In the Third Branch, Manawydan and his companions sit on the same mound and a great clap of thunder and a mist fall; when it clears, every house, beast and person in Dyfed has vanished except themselves. The mythical mound has never been identified, though several sites have been suggested. Wirt Sikes remarked in 1880 that the places named in the tales were still familiar to local people.
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